When considering the role of neuroscience in modern society, the issue of a brain-machine interface (e.g., between a human brain and a computer) is one of the central problems to be addressed. Indeed, the ability to design and build new information analysis and storage systems that are light enough to be easily carried, has advanced exponentially in the last few years. Ultimately, the brain-machine interface will likely become the major stumbling block to robust and rapid communication with such systems.
To date, developments towards a brain-machine interface have not been as impressive as the progress in miniaturization or computational power expansion. Indeed, the limiting factor with most modern devices relates to the human interface. For instance, buttons must be large enough to manipulate and displays large enough to allow symbol recognition. Clearly, establishing a more direct relationship between the brain and such devices is desirable and will likely become increasingly important.
With conventional means, brain activity can be recorded from the surface of the skull. In the case of electro-encephalography (EEG), electrodes are placed on the skull and record activity occurring on the surface of the brain. In the case of magneto-encephalography (MEG), recording probes are also placed on the surface, but through triangulation brain activity can be mapped in three dimensions.
Such methods as EEG and MEG, while minimally invasive, suffer from poor resolution and distortion due to the deformation of electromagnetic fields caused by the scalp and skull. To overcome these limitations with known technology requires the much more invasive option of opening the skull and inserting electrodes into the brain mass. Similarly, to stimulate the brain as is done therapeutically for some patients with Parkinson's disease or the like, the skull must be opened and electrodes inserted.
As the need for a more direct relationship between the brain and machines becomes increasingly important, a revolution is taking place in the field of nanotechnology (n-technology). Nanotechnology deals with manufactured objects with characteristic dimensions of less than one micrometer. It is the inventors' belief that the brain-machine bottleneck will ultimately be resolved through the application of nanotechnology. The use of nanoscale electrode probes coupled with nanoscale electronics seems promising in this regard.
To date, the finest electrodes have been pulled from glass. These microelectrodes have tips less than a micron in diameter and are filled with a conductive solution. They are typically used for intracellular recordings from nerve and muscle cells. A limitation is that activity is recorded from only one cell at a time. It has been possible, however, to obtain recordings from over 100 individual cells using multi-electrode arrays. Nonetheless, this is an invasive procedure as the electrodes are lowered into the brain from the surface of the skull.
In addition to probing large numbers of points in the brain, the need also exists for processing the large number of signals thus captured and analyzing them in a meaningful way. Methods for processing and displaying signals from multiple sites within the brain have been developed for multi-electrode work with animals and for MEG work with human subjects
What is required is a robust and non-invasive way to tap, address and analyze brain activity that is optimized for future brain-machine interaction.
In addition to serving as a means of interacting with machines, a brain-machine interface could also be useful in the diagnosis and treatment of many neurological and psychiatric conditions.